all that is filtered at the glomerulus appears in urine, and all that is in urine is due to glomerular filtration) It must be neither reabsorbed from the filtrate to blood nor secreted from blood to the filtrate by renal tubulecells (i.e.It must be freely filtered from blood at the glomerulus.It must be excreted only by the kidneys.kidney function) declines, urinary excretion of urea and creatinine also declines and blood concentration of both increases.įor the blood concentration of an endogenously produced substance to most accurately reflect GFR in health and disease, that substance must have the following properties: Irrespective of its cause, kidney disease is associated with decrease in GFR, and the severity of kidney disease correlates closely but inversely with GFR.Ī normal GFR (~125 mL/min) is presumptive evidence of healthy, functioning kidneys. The rationale for the use of creatinine or urea measurement to assess renal function is that plasma/serum levels of both reflect glomerular filtration rate (GFR), the parameter that defines kidney function for the clinician. If kidney damage is a concern, ask your doctor what factors may be contributing to the damage and what steps you can take to try to control them.Creatinine and urea blood levels reflect glomerular filtration rate (GFR) Certain medications, such as some antibiotics.Congestive heart failure or recent heart attack.Dehydration, resulting from not drinking enough fluids or for other reasons.Generally, a high BUN level means your kidneys aren't working well. Infants have lower levels than other people do, and the range in children varies. Urea nitrogen levels tend to increase with age. In general, around 6 to 24 mg/dL (2.1 to 8.5 mmol/L) is considered normal.īut normal ranges may vary, depending on the reference range used by the lab and your age. Results of the BUN test are measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) internationally. You can return to your usual activities immediately. The blood sample is sent to a lab for analysis. What you can expectĭuring the BUN test, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm. Your doctor will give you specific instructions. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test.

If your blood sample is being tested only for BUN, you can eat and drink normally before the test. The GFR estimates the percentage of kidney function you have. To do this, you may have a blood sample taken to calculate your estimated glomerular filtration rate (GFR). Your doctor may also test how well your kidneys are removing waste from the blood. High levels of creatinine in your blood may be a sign of kidney damage. Creatinine is another waste product that healthy kidneys filter out of your body through urine. If kidney problems are the main concern, the creatinine levels in your blood will likely also be measured when your blood is tested for urea nitrogen levels. As part of a blood test group to help diagnose a number of other conditions, such as liver damage, urinary tract obstruction, congestive heart failure or gastrointestinal bleeding - although an abnormal BUN test result alone doesn't confirm any of these conditions.To help determine the effectiveness of dialysis treatment if you're receiving hemodialysis or peritoneal dialysis.If your kidney function needs to be evaluated, especially if you have a chronic condition such as diabetes or high blood pressure.If your doctor suspects that you have kidney disease or damage.

Bun creat ratio normal range